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Municipal wastewaters contain a multitude of organic trace pollutants. Often, their biodegradability by activated sludge microorganisms is decisive for their elimination during wastewater treatment. Since the amounts of micropollutants seem too low to serve as growth substrate, cometabolism is supposed to be the dominating biodegradation process. Nevertheless, as many biodegradation studies were performed without the intention to discriminate between metabolic and cometabolic processes, the specific contribution of the latter to substance transformations is often not clarified. This minireview summarizes current knowledge about the cometabolic degradation of organic trace pollutants by activated sludge and sludge-inherent microorganisms. Due to their relevance for communal wastewater contamination, the focus is laid on pharmaceuticals, personal care products, antibiotics, estrogens, and nonylphenols. Wherever possible, reference is made to the molecular process level, i.e., cometabolic pathways, involved enzymes, and formed transformation products. Particular cometabolic capabilities of different activated sludge consortia and various microbial species are highlighted. Process conditions favoring cometabolic activities are emphasized. Finally, knowledge gaps are identified, and research perspectives are outlined.

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IntroductionThe appropriate treatment of type II and III odontoid fractures still remains controversial. However in the recent literature there seems to be a tendency to opt for primary internal fixation with interfragmentary screws [1,7,8,19,23,29,36]. The reported rate of non-union varies between 2.4% and 100% for all types of fractures and treatment modalities, with the highest rates for untreated fractures and fractures treated with a cervical collar only. Important factors reported to contribute to non-union of these fracAbstract Despite various reports on the management of odontoid fractures, there is no consensus on the subject, and the appropriate treatment still remains controversial. While untreated fractures or fractures treated only with a cervical orthosis seem to have the highest rate of nonunion, the need for rigid external stabilisation has never been substantiated. In a retrospective analysis we reviewed 26 patients with acute type II and III fractures of the odontoid, treated with a cervical orthosis only. Study inclusion was limited to fractures that had a fracture gap of less than 2 mm, an initial antero-posterior displacement of less than 5 mm and angulation of less than 11°, less than 2 mm displacement on lateral flexion/extension views, and were without neurological deficits. These fractures were defined as stable. There were 19 (73.1%) type II and 7 (26.9%) type III fractures; in 10 (38.5%) of these fractures the odontoid was displaced and/or angulated. The overall complication rate was 11.4% (n=3). One patient suffered from pulmonary embolism, in two patients (7.7%) with initially minimally displaced fractures, secondary internal stabilisation had to be performed because of persistent instability. In 20 (77%) of the remaining fractures healing was uneventful. In 4 nondisplaced fractures (15%) fibrous union was documented. Three of these patients were over 65 years old. The overall fusion rate was 73.7% for type II and 85.7% for type III fractures. At follow-up 39% of the patients were free of symptoms; however, the clinical outcome did not correlate with the radiological findings. According to our findings, stable type II and type III fractures of the odontoid can be successfully treated with non-rigid immobilisation, even if they are displaced. A thorough assessment of the stability of the odontoid with lateral flexion/extension views or dynamic fluoroscopy is recommended to evaluate the appropriate treatment. Nonrigid immobilisation may be an option in selected cases with stable injuries.